<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        button{
            background-color: orange;
            color: orchid;
            font-size: 15px;
        }
    </style>
</head>
<body>
   
        <button id="btn">btn</button>
        <script>
            var btn = document.getElementById("btn");
            btn.onclick = function(){
                this.innerHTML = "60";
                this.style.backgroundColor = "lightblue";
                this.style.color = "red";
                this.style.fontSize = "20px"
            }
           
        </script>
</body>
</html>